Earlier this month, Caplin, a 100-pound capybara, decided to speak up for his species.

"Stupid Pope said we are fish. ...How can capybaras legally be eaten at Lent? They're MEAT?," his Twitter account said. "Long ago Pope thought Venezuelans won't be Catholic if have to eat real fish so declared capybara fish. We hates that."

Melanie Typaldos, Caplin's owner (and Twitter typist), said her husband started their pet's Twitter account about a year ago. Caplin has more than 3,000 followers and uses Twitter to set the record straight on the capybara, the world's largest rodent.

Typaldos, a 54-year-old engineer from Buda, Texas, who has also written a book on capybaras, said she tweets whatever she thinks Caplin might be thinking. (And, incidentally, she added, "Capybaras do 'tweet.' They make a sound very much like a bird.")

"On Twitter, he's pretty upset because it's Lent now and the pope declared that people eat a lot of capybara," she said.

Caplin also sticks up for his smaller rodent brethren.

"He's rodent royalty and the protector of all rodents," she said. "He gets involved in conversations about rodents. Rodents are not really popular on Twitter. They do say mean things and he'll stand up for them."

Dogs, Cats Have Virtual Play Dates Online

In 140-character squawks, barks and chirps, pet lovers from around the world have taken on their animals' personas to talk, tease and even raise money for the animals they love.

"It's like a virtual version of what people do when they set up a play date with dogs or get together in the park," said Gregory Galant, founder of Sawhorse Media, which created Pet Feed, a dedicated Web site for "pets on Twitter."

When they launched the site last spring, he said, the site included hundreds of users. Now, he estimates that the number of pets on Twitter has grown tenfold. And it's not just your run-of-the-mill cats and dogs that tweet. Ferrets, fish, horses, turtles, rabbits, birds and, of course, capybaras, are all represented online.

With more than 1.5 million followers, Sockington is arguably Twitter's most popular animal. On a site that calls its messages "tweets," Schwartz (and Rudy) believe that's unfair.

"In those early days, Rudy spent much of his time lamenting the number of followers Sockington had amassed. At 20,000 Rudy called him the 'Wilt Chamberlain of cats.' At 50,000 he likened it to a virus that could soon reach the White House," Schwartz said.

In tweeted pleas to the Animal Planet's Twitter feed and letters to the editor of the New York Times, Schwartz has documented Rudy's mock campaign to unseat Sockington, which he calls "The Resistance."

Still, Schwartz acknowledged that the bird and cat have a "love hate relationship" on Twitter, since Rudy owes many of his followers to the "Sockington effect." In one day, he said, Rudy's account gained hundreds of followers after Sockington mentioned him in a tweet.